Rock and Stone!
Common42.3%ObjectiveMissable
You killed an enemy with a boulder dropped from the battlements. Karl would be proud!
A one-off kill during a fortress-defence sequence - there's a boulder up on the battlements you can send down onto attackers below, and dropping it on an enemy is the trophy. It's easy to blow past the moment in the heat of the fight, so when you're up on the walls look for the loose boulder and use it on someone before the section ends.